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Selenium (Se) and iodine (I) are essential elements for humans, and biofortification of vegetables with these elements is an effective way to amend their deficiencies in the diet. In this study, the distribution and transformation of Se and I species were investigated in radish seedlings that were simultaneously supplemented with these two elements; the fate and the bioaccessibility of Se and I species were dynamically surveyed in the oral, gastric and intestinal phases using a simulated in vitro digestion method. The radish seedlings were cultivated in hydroponic conditions with Se (IV), Se (VI), I− and IO3− (each 1 mg L−1). The results revealed that Se-methylselenocysteine (MeSeCys), selenocystine (SeCys2), selenomethionine (SeMet) and Se (VI) were present in radish, and MeSeCys was the dominant species in both gastric and intestinal extracts, comprising 32.7 ± 1.5% and 39.6 ± 1.1% of the total content, respectively. I− was also the dominant species, which accounted for 57.1 ± 2.1%, 46.6 ± 1.5% and 68.8 ± 1.8% of the total digested content respectively in the oral, gastric and intestinal extracts. Meanwhile, IO3− was absent and organic I accounted for approximately 20%. The bioaccessibility of Se and I in the intestinal phase reached 95.5 ± 2.5% and 85.8 ± 0.9%, respectively; although after dialysis through membranes, the data reduced to 60.1 ± 2.8% and 39.6 ± 0.8%, respectively. Contents of MeSeCys and I− increased from the oral to intestinal phase and the bioaccessibility of both Se and I in radish was above 85%. So radish is suitable as a potential dietary source of Se and I with biofortification.

Biological soil crusts (BSCs) hold promise for reducing soil erosion in subtropical forest plantations, and microorganisms profoundly affect the formation and development of BSCs. The effects of biochar as a soil conditioner on the diversity and structure of soil microbial communities in BSCs are largely unknown. Therefore, our aim was to determine how biochar might improve microbial community composition and BSC function. Herein, a field experiment was conducted in a P. massoniana plantation; the addition of biochar was the treatment, and no biochar addition was the control (CK). Soil microbial communities associated with moss BSCs (in and beneath BSCs) with and without the addition of biochar were analyzed by Illumina sequencing technology. The results showed that Acidobacteria (28.35%), Proteobacteria (22.53%), Actinobacteria (17.41%), and Chloroflexi (16.74%) were the dominant bacterial phyla, whereas Basidiomycota (70.00%) and Ascomycota (22.76%) were the dominant fungal phyla in BSCs. The soil bacterial and fungal OTU number and richness in BSCs were higher than those beneath BSCs. The relative abundances of Acidobacteria, Chloroflexi, and Basidiomycota were higher in BSCs than beneath BSCs, whereas the relative abundances of Actinobacteria, Firmicutes, Ascomycota, and Chytridiomycota showed the opposite trend. Beneath BSCs, biochar addition increased the soil bacterial OTU number and richness (ACE index and Chao1) but decreased the soil fungal OTU number and richness. Biochar had little effect on soil microbial community structures in BSCs; however, beneath BSCs, it significantly increased the relative abundances of Acidobacteria, Chloroflexi, and Basidiomycota and significantly decreased the relative abundances of Actinobacteria, Firmicutes, Ascomycota, and Chytridiomycota. Biochar-induced changes in soil microbial communities were related to soil environmental factors, especially urease activity, organic matter content, pH, total nitrogen content, and sucrase activity. We demonstrated the different effects of biochar on soil microbial communities in and beneath the BSCs of subtropical forest plantations; these findings provided new insights into soil stabilization with BSCs below the forest canopy in subtropical regions.

Consuming arsenic (As)-contaminated vegetables is the main route of As exposure in humans. The present study focused on the alterations in antioxidant enzymatic activities and As bioaccessibility in As-contaminated radish subjected to Se. Compared to the CK group, the total As content in raw radish was reduced by 27.5 ± 1.3%, and the bioaccessibility of As was reduced by 21.9 ± 2.3% in the 6 mg Se kg−1 treatment group. The total As content in the treatment groups decreased first but then increased with increasing Se application in raw radish, gastric (G) fraction and gastrointestinal (GI) fraction, while the antioxidant activity exhibited the opposite trend. The results revealed that a low amount of Se effectively blocks the accumulation of As in radish, improves the antioxidant activity in radish and reduces the bioaccessibility of As. These findings provide new ideas for effectively alleviating the spread of As to the human body through the food chain.

Consumption of arsenic (As)-contaminated vegetables is a major As exposure pathway for humans. However, little is known about plant As uptake characteristics and the bioaccessibility of As after ingestion of As-contaminated radish. The present study investigated As concentrations and species in As-contaminated radish and assessed the effects of steamed, griddled and boiled cooking on the bioaccessibility of As in radish using in vitro digestion. The results showed that the radish accumulated 46.3 ± 2.3, 79.2 ± 1.2 and 113.2 ± 3.7 μg As g-1 when treated with 0.5 mg L-1 As(iii) + 0.5 mg L-1 As(v), 1.0 mg L-1 As(iii) + 1.0 mg L-1 As(v) and 2.0 mg L-1 As(iii) + 2.0 mg L-1 As(v), respectively, in culture solution. In both gastric (G) and gastrointestinal (GI) fractions, the total As and species contents in radish decreased in the following order: raw > steamed > griddled > boiled. The bioaccessibility of total As was 97.5 ± 1.2%, 89.3 ± 1.3%, 84.8 ± 1.2% and 52.1 ± 1.1% in the GI phase when the radish was raw, steamed, griddled and boiled, respectively, and the bioaccessibility was not more than 60.1 ± 2.3% in the G phase. These data suggested that boiled cooking should be recommended for consumption of As-contaminated radish because it reduces total As and its species by approximately 50%. Additionally, organic As forms and factors influencing the bioaccessibility of As should be further studied to scientifically evaluate the health risks of As in radish.

Background and aims Tropical and subtropical forests are experiencing high levels of atmospheric nitrogen (N) deposition, but the responses of such forests ecosystems to N deposition remain poorly understood.

The nutrient accumulation and cycling were investigated from 2-to 6-year-old Eucalyptus urophylly × E.grandis plantations in the southern mountain region of Fujian Province,China.The results showed that N content was the highest in the tree components,followed by K,Ca,Mg and P.N content in the 2-,3-,4–year-old stands decreased,then increased slightly in the 5-and 6-year-old stands.The nutrient accumulations were 753.26,882.07,1 010.22,1 087.51,1 704.79 kg hm-2 in the 2-,3-,4-,5-and 6-year-old stands,respectively.Annual net nutrient accumulation was highest(505.36 kg hm-2) in the 6-yearold stand,and in the 2-,3-,4-,and 5-year-old stands,the values were 383.37,392.25,424.21,400.89 kg hm-1 a-1,respectively.The nutrient absorption increased along stand age while nutrient return showed a decreased trend.The coefficients of nutrient utilization were 0.51,0.44,0.42,0.37,0.30 along the forest age.The nutrient cycling coefficients did not show obvious trend with the values from 0.16 to 0.24.The recycling period of nutrients was 8.76,9.75,7.58,9.39,17.47 years along with stand age,respectively.The results indicate that Eucalyptus urophylly × E.grandis plantations have low nutrient utilization efficiency in the early stage while have high nutrient utilization efficiency.Nutrient deficient would limit biomass accumulation in these plantations and fertilization management should be considered.